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Siblingship DNA Testing, Does It Work?

DNA testing between two or more people who believe they could be siblings is referred to as sibship, or siblingship testing. This type of relational test compares the genetic profile of the individuals who believe they could share one or both parents. Often times, the alleged siblings will use the sibship test to determine if they have the same father. Thus, it also can be referred to as a sibling paternity test.

When choosing a company to handle your important family questions, pricing isn’t everything. It’s important to make sure the lab is accredited by the AABB, formerly known as the American Association of Blood Banks, which is the accrediting agency trusted by courts all over the country. Recently, a number of new tests are being advertised by some companies that claim to be able to test more markers and “guarantee” conclusive results, however there is only one test that is AABB accredited. The accredited test, which is sold by companies like Paternity-USA, compares 16 genetic markers, and depending on which markers match, the result is calculated into a percentage of probability of the biological relationship, as with most other DNA tests.

The most common use for the siblingship test is to determine if two people have the same father. It is always best for the father to participate in a paternity test if he is available. The paternity test will give basically a “yes” or “no” answer, where a sibling test is not as precise. Adoptions and genealogy research are another common reason a siblingship test may be necessary. Many folks will find someone that could be a long lost brother or sister, years after the fact, and just want to make sure they are truly related.
When the tested siblings are known to have different mothers, it is especially important to add the mothers’ DNA to the test. With the mothers’ participation, each mother’s profile is compared to their child’s profile, and hence eliminating the genetic material that is not useful in the evaluation. This leaves only the genes that the father donated to each person, and then those markers are compared to give what is usually a very conclusive result. If the mother or mothers are not available for sampling, the test can still be done, however the result may not be as high or low of a percentage.

The analysis will basically start at 50% and when the genetic material is evaluated for matches, the percentage either goes up or down. How much the percentage changes from that beginning 50% point depends upon how many and which genetic markers match. Some markers have more weight than others, and those are called “multiplier” markers.

If the two siblings are known to have the same mother, inclusion of that mother is not quite as important and the test can still be conclusive without her participation. If the test participants are known to be at best half-siblings, it is very important to include one or both mothers to eliminate as much of the unwanted DNA as possible. Again, the test can still be performed however the result may not be as conclusive and could leave lingering questions after the process.

In conclusion, the most important things to consider with sibship testing are the quality of the test and lab, and the inclusion of the known parent(s). These two factors can make or break the testing process and results.

Consider how fast the world of technology changes. What may not have been possible yesterday may be possible today. Likewise, what may not be possible today could be possible tomorrow. The science and technology behind DNA testing is also ever-changing and evolving. Make sure you choose a company like Paternity-USA that offers accredited testing.